1. Field of the Invention
The present invention relates to a Voice over Internet Protocol (VoIP) system, and more particularly, to a method for call processing and link test in a Voice over Internet Protocol (VoIP) Gateway and system thereof, capable of dispersing gatekeeper traffic and improving service quality at the same time, by distinguishing whether or not a gatekeeper has been used in accordance with an access code (e.g. trunk code or area code) and performing a link test and Voice over Internet Protocol (VoIP) call processing.
2. Description of the Related Art
As the name implies, Voice over Internet Protocol (VoIP) is a communication technology using Internet protocol and provides voice call service, multimedia video conference and so forth. Because of interworking between an IP (Internet Protocol) network and a Public Switch Telephone Network (PSTN), application of Voice over Internet Protocol (VoIP) has also been expanded to a variety of equipment and application services. That is, a VoIP service sends videos, voices, and fax messages over the Internet, and uses a real-time protocol (RTP) to help ensure that packets get delivered in a timely way when transmitting real-time media such as voices and videos; and in many cases when a user who wants to use the Internet, access to the Internet is provided by a PC (Personal Computer) or by using an independent device (e.g., Internet phone) applied with an Internet protocol (IP), by making a call to a Gateway from an existing PSTN (Public Switched Telephone Network) terminal.
To perform the VoIP service, a unit for searching the other party and signaling is necessary. There are two kinds of VoIP signaling units, such as H.323 of ITU-T (International Telecommunication Standardization Sector) and an SIP (Session Initiation Protocol) of IETF (Internet Engineering Task Force).
A VoIP service network is divided into two kinds, namely a network being operated using a gatekeeper and a network being operated without a gatekeeper.
In general, a network is a series of points or nodes interconnected by communication paths. Networks can interconnect with other networks and contain subnetworks. The most common topology or general configurations of networks include the bus, star, and token ring topologies. Networks can also be characterized in terms of spatial distance as local area networks (LAN), metropolitan area networks (MAN), and wide area networks (WAN). A given network can also be characterized by the type of data transmission technology in use on it (for example, a TCP/IP or Systems Network Architecture network); by whether it carries voice, data, or both kinds of signals; by who can use the network (public or private); by the usual nature of its connections (dial-up or switched, dedicated or nonswitched, or virtual connections); and by the types of physical links (for example, optical fiber, coaxial cable, and Unshielded Twisted Pair).
Large telephone networks and networks using their infrastructure (such as the Internet) have sharing and exchange arrangements with other companies so that larger networks are created. A Gateway is a network point that acts as an entrance to another network. On the Internet, a node or stopping point can be either a Gateway node or a host (end-point) node. Both the computers of Internet users and the computers that serve pages to users are host nodes. The computers that control traffic within your company's network or at your local Internet service provider (ISP) are Gateway nodes. In the network for an enterprise, a computer server acting as a Gateway node is often also acting as a proxy server and a firewall server. On the Internet, a node or stopping point can be either a Gateway node or a host (end-point) node. Both the computers of Internet users and the computers that serve pages to users are host nodes. The computers that control traffic within a company's network or at a local Internet service provider (ISP) are Gateway nodes.
A gatekeeper is located between the Internet and a Gateway. A Gateway is often associated with both a router, which knows where to direct a given packet of data that arrives at the Gateway, and a switch, which furnishes the actual path in and out of the Gateway for a given packet. The gatekeeper's major functions include address translation for enabling voice calls between terminals (endpoints) by converting an alias (H.323 identifier, URL, phone number or e-mail address) to a transport address (IP address), and managing the status of remote (destination) Gateways and performing call routing processes accordingly.
To explain the network without gatekeeper first, a Gateway directly performs a link test on a remote (destination) Gateway to check the status of the remote Gateway. In this case, the Gateway performs the link test on every routable Gateway and checks their states, respectively.
On the other hand, when a gatekeeper is used, the gatekeeper manages each Gateway's channel information and status so there is no need for the Gateway to perform the link test itself.
Depending on what kind of Gateway is used, the Gateway using a gatekeeper can be operated in auto Registration/Admission/Status (RAS) mode or in manual Registration/Admission/Status (RAS) mode.
For one's information, Registration/Admission/Status (RAS) is a protocol involved with basic call routing (or call processing) operation between a gatekeeper and each terminal, or endpoint, (Gateway, H.323 terminal, MCU and the like) based on H.225 Call Signaling Protocol.
In auto RAS mode, the gatekeeper is absolutely used regardless of an access code of a telephone number (alias) being received to the Gateway, and in manual RAS mode, on the other hand, the gatekeeper may be or may not be used depending on the access code.
The following details the manual RAS mode that is dealt with primarily by the present invention.
The manual RAS mode provides RAS conditionally. For instance, if one makes a local Voice over Internet Protocol (VoIP) call to someone in a different place of the same company, the gatekeeper is not necessary because the call is free of charge.
On the other hand, if one makes a phone call to someone in another company through a Public Switched Telephone Network (PSTN), the call is charged for using the Public Switched Telephone Network (PSTN). Thus the gatekeeper needs to route a Voice over Internet Protocol (VoIP) call being currently made.
However, the Gateway in the manual RAS mode, despite of the access code using the gatekeeper, should perform the link test on the remote Gateway following the manual RAS, only causing a heavy traffic in the network.